U.S. patent number 5,441,027 [Application Number 08/208,365] was granted by the patent office on 1995-08-15 for individual timing and injection fuel metering system.
This patent grant is currently assigned to Cummins Engine Company, Inc.. Invention is credited to David L. Buchanon, Julius P. Perr, Lester L. Peters, Yul J. Tarr.
United States Patent |
5,441,027 |
Buchanon , et al. |
August 15, 1995 |
Individual timing and injection fuel metering system
Abstract
A metering system is provided which controls the amount of fuel
supplied to the combustion chambers of a multi-cylinder internal
combustion engine comprising a fuel pump for supplying fuel at low
pressure to a first and a second group of unit fuel injectors, a
first solenoid-operated fuel control valve controlling the flow of
fuel to the first set of injectors and a second solenoid-operated
fuel control valve controlling the flow of fuel to the second set
of injectors. The system may also include first and second
solenoid-operated timing fluid control valves associated with the
first and the second group of injectors, respectively. The
injectors are capable of being in the fuel receiving mode,
establishing a metering period, and the timing receiving mode,
establishing a timing period, at the same time to increase the
amount of time available for metering both timing fluid and fuel.
By grouping the various injectors based on the order of injection
so that the injectors from each group are placed in the injection
mode in spaced periods throughout each cycle of the engine, e.g.
injectors from other groups injecting in the period of time between
each injection mode, the system can be designed to permit longer
metering and timing periods.
Inventors: |
Buchanon; David L. (Westport,
IN), Peters; Lester L. (Columbus, IN), Perr; Julius
P. (Columbus, IN), Tarr; Yul J. (Columbus, IN) |
Assignee: |
Cummins Engine Company, Inc.
(Columbus, IN)
|
Family
ID: |
26745761 |
Appl.
No.: |
08/208,365 |
Filed: |
March 10, 1994 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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65583 |
May 24, 1993 |
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Current U.S.
Class: |
123/446; 123/456;
123/500; 123/510 |
Current CPC
Class: |
F02M
57/02 (20130101); F02M 57/021 (20130101); F02M
57/024 (20130101); F02M 57/025 (20130101); F02M
57/026 (20130101); F02M 59/105 (20130101); F02M
59/366 (20130101) |
Current International
Class: |
F02M
59/36 (20060101); F02M 59/00 (20060101); F02M
57/00 (20060101); F02M 59/20 (20060101); F02M
57/02 (20060101); F02M 59/10 (20060101); F02M
057/02 (); F02M 059/36 () |
Field of
Search: |
;123/446,502,456,500,501,510,481 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1522293 |
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Feb 1967 |
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FR |
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57-68532 |
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Apr 1982 |
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JP |
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2030222 |
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Apr 1980 |
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GB |
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Other References
Patent Abstracts of Japan, Publication No. JP58131338, vol. 7, No.
244 "Fuel Supplying Apparatus for Diesel Engine", Aug. 1993. .
Patent Abstracts of Japan, Publication No. JP57168051, vol. 7, No.
9 "Fuel Injection System", Oct. 1982..
|
Primary Examiner: Moulis; Thomas N.
Attorney, Agent or Firm: Sixbey, Friedman, Leedom &
Ferguson
Parent Case Text
This Application is a Continuation-In-Part of Ser. No. 08/065,583,
now abandoned, filed May 24, 1993.
Claims
We claim:
1. A metering system for controlling the amount of fuel supplied to
the combustion chambers of a multi-cylinder internal combustion
engine, comprising:
a fluid supply means for supplying fuel at low supply pressure,
said fluid supply means including first and second fuel supply
paths;
a first set of unit injectors for receiving fuel from said fluid
supply means at the low supply pressure and for injecting the fuel
at relatively high pressure into respective combustion chambers of
the engine, each injector of said first set adapted to be placed in
a fuel receiving mode for receiving fuel from said fluid supply
means, only one unit injector from said first set of unit injectors
being placed in said fuel receiving mode at any given time;
a first electromagnetic fuel control valve positioned in said first
fuel supply path between said fluid supply means and said first set
of unit injectors for controlling the flow of fuel to said first
set of unit injectors;
a second set of unit injectors for receiving fuel from said fluid
supply means at the low pressure and for injecting the fuel at
relatively high pressure into respective combustion chambers of the
engine, each injector of said second set adapted to be placed in a
fuel receiving mode for receiving fuel from said fluid supply
means, only one unit injector from said second set of unit
injectors being placed in said fuel receiving mode at any given
time; and
a second electromagnetic fuel control valve positioned in said
second fuel supply path between said fluid supply means and said
second set of unit injectors for controlling the flow of fuel to
said second set of unit injectors.
2. The metering system of claim 1, wherein said fluid supply means
includes first and second timing fluid supply paths for supplying
timing fluid to said first and said second set of unit injectors,
respectively, each unit injector of said first and said second set
of unit injectors adapted to receive timing fluid from said fluid
supply means for controlling the timing of injection, further
including a first electromagnetic timing fluid control valve
positioned in said first timing fluid supply path between said
fluid supply means and said first set of unit injectors for
controlling the flow of timing fluid to said first set of unit
injectors, and a second electromagnetic timing fluid control valve
positioned in said second timing fluid supply path between said
fluid supply means and said second set of unit injectors for
controlling the flow of timing fluid to said second set of unit
injectors, wherein at any given time during the operation of the
unit injectors only one unit injector from each of said first and
said second set of unit injectors is in a timing fluid receiving
mode for receiving timing fluid from said fluid supply means.
3. The metering system of claim 2, wherein said one unit injector
is capable of being in said fuel receiving mode and said timing
fluid receiving mode at the same time.
4. The metering system of claim 2, wherein each unit injector
includes an injector body containing an injector cavity, a fluid
timing circuit communicating with one of said first and said second
timing fluid supply paths, and a fuel metering circuit
communicating with one of said first and said second fuel supply
paths, said fluid timing circuit and said fuel metering circuit
communicating with said injector cavity, and an injection orifice
formed in one end of said injector body and further including a
plunger means mounted for reciprocal movement within said injector
cavity, said plunger means comprising inner and outer plunger
sections, a variable volume timing chamber being formed in said
injector cavity between said inner and outer plunger sections and a
variable volume fuel metering chamber being formed in said injector
cavity between said inner plunger section and said injection
orifice and wherein said plunger means is operable to be placed in
said fuel receiving mode establishing a metering period during
which fuel may flow through said metering circuit into said
metering chamber, is operable to be placed in said timing fluid
receiving mode establishing a timing period during which timing
fluid may flow through said fluid timing circuit into said timing
chamber, and is operable to be placed in an injection mode in which
fluid flow through both circuits to both of said chambers is
blocked thereby for producing injection of the fuel in said
metering chamber through said injection orifice.
5. The metering system of claim 4, wherein at least a portion of
said metering period of each unit injector occurs during said
timing period of the same unit injector.
6. The metering system of claim 4, wherein said first and said
second electromagnetic fuel control valves are each movable between
an open position wherein fuel may flow therethrough to said
metering chamber of a unit injector of said first set of unit fuel
injectors and said second set of unit fuel injectors, respectively,
during said metering period and a closed position wherein fuel is
blocked from flowing therethrough to said metering chamber, and
wherein said first and said second electromagnetic timing fluid
control valves are each movable between an open position wherein
timing fluid may flow therethrough to said timing chamber of a unit
injector of said first set of unit fuel injectors and said second
set of unit fuel injectors, respectively, during said timing period
and a closed position wherein fluid is blocked from flowing
therethrough to said timing chamber.
7. The metering system of claim 6, wherein each of said first and
said second electromagnetic fuel control valves and each of said
first and said second electromagnetic timing fluid control valves
is movable from said closed position to said open position and from
said open position to said closed position within said metering
period and said timing period, respectively, to define a fuel
metering event and a timing fluid metering event, respectively.
8. The metering system of claim 7, wherein said plunger means is
operable to move through periodic injection Strokes in which said
plunger means moves inwardly in said injector cavity toward said
injection orifice for each cycle of the engine causing fuel to be
expelled from said injector cavity through said injection orifice
to the combustion chamber, said fuel metering event and said timing
fluid metering event occurring only between said periodic injection
strokes.
9. The metering system of claim 7, wherein said plunger means is
operable to move through a metering stroke in which said plunger
means moves outwardly in said injector cavity away from said
injection orifice, said fuel metering event and said timing fluid
metering event occurring only during said metering stroke.
10. The metering system of claim 1, wherein each unit injector of
said first and said second set of unit injectors includes an
injector body containing an injector cavity, a fluid timing circuit
for receiving timing fluid from said fluid supply means, a fuel
metering circuit communicating with one of said first and second
fuel supply paths, a plunger means mounted for reciprocal movement
within said injector cavity and an injection orifice formed in said
injector body at one end of said injector cavity, a variable volume
metering chamber being formed in said injector cavity adjacent a
first end of said plunger means between said plunger means and said
injection orifice and a variable volume timing chamber being formed
in said injector cavity adjacent a second end of said plunger means
opposite said first face, said timing chamber of each injector
adapted to receive timing fluid from said fluid supply means,
further including an electromagnetic timing fluid control valve
positioned in said fluid timing circuit between said timing chamber
and said fluid supply means for controlling the flow of timing
fluid to said timing chamber, wherein said electromagnetic timing
fluid control valve is movable between an open position wherein
timing fluid may flow therethrough to said timing chamber and a
drain position wherein timing fluid is drained therethrough from
said timing chamber to define a timing event during which the
timing fluid at a predetermined pressure forces said plunger means
toward said metering chamber for producing injection of the fuel in
said metering chamber through said injection orifice.
11. The metering system of claim 10, wherein the timing fluid acts
on said second end of said plunger means to force said plunger
means toward said metering chamber, said second end having an
effective cross-sectional area greater than the effective
cross-sectional area of said first end of said plunger means.
12. The metering system of claim 4, wherein said fuel metering
circuit includes a fuel supply port formed in said injector body
and a spring-loaded check valve positioned upstream of said supply
port for permitting fuel to flow into said metering chamber during
said metering period and for preventing the flow of fuel from said
metering chamber during the period of injector operation when the
metered fuel is injected.
13. The metering system of claim 12, wherein said inner plunger
section reciprocates adjacent to said injection orifice and said
metering chamber is positioned adjacent said injection orifice.
14. The metering system of claim 2, wherein said fluid supply means
supplies timing fluid to said first and said second timing fluid
supply paths at a substantially constant pressure and supplies fuel
to said first and said second fuel supply paths at a substantially
constant pressure.
15. The metering system of claim 2, wherein said fluid supply means
includes a fuel pump for providing fuel to each of said first and
said second fuel supply paths and to each of said first and said
second timing fluid supply paths.
16. The metering system of claim 15, wherein said fuel pump
includes a pressure regulator for varying the fuel supply pressure
based on engine operating conditions.
17. The metering system of claim 15, further including at least one
flow control valve positioned downstream of said fuel pump for
providing a fixed fuel flow rate independent of fuel pressures
upstream and downstream of said at least one flow control
valve.
18. The metering system of claim 17, wherein said at least one flow
control valve includes four flow control valves, each of said four
flow Control valves positioned adjacent one of said electromagnetic
valves.
19. The metering system of claim 1, wherein each injector of said
first and said second set of injectors is adapted to be placed in a
fuel injection mode for producing injection of the fuel into
respective combustion chambers of the engine, said injection mode
of each injector in said first set of injectors occurring after the
injection mode of an injector of said second set of injectors.
20. The metering system of claim 2, wherein said first and second
timing fluid supply paths are fluidically separate from said first
and second fuel supply paths.
21. The metering system of claim 20, wherein said fluid supply
means includes a lube oil supply pump for supplying lube oil to
said timing fluid supply paths and a fuel supply pump for supplying
fuel to said first and second fuel supply paths.
22. A metering system for metering and timing of fuel injection
into the combustion chambers of a multi-cylinder internal
combustion engine, comprising:
a fluid supply means for supplying fuel and timing fluid at a low
supply pressure, said fluid supply means including a timing fluid
common rail and a fuel common rail;
one or more unit injectors positioned adjacent said common rails
for receiving fuel at the low supply pressure and for injecting the
fuel at relatively high pressure into respective combustion
chambers of the engine, each of said one or more injectors
including an injector body containing an injector cavity, a fluid
timing circuit communicating with said timing fluid common rail, a
fuel metering circuit communicating with said fuel common rail, and
an injection orifice formed in one end of said injector body and
further including a plunger means mounted for reciprocal movement
in said injector cavity, said plunger means including inner and
outer plunger sections, a variable volume timing chamber being
formed in said injector cavity between said inner and outer plunger
sections and a variable volume fuel metering chamber being formed
in said injector cavity between said inner plunger section and an
end of the injector cavity;
an electromagnetic timing fluid control valve positioned in said
timing fluid common rail for controlling the flow of fuel to said
timing chamber, said electromagnetic timing fluid control valve
being movable between an open position wherein timing fluid may
flow therethrough to said timing chamber and a closed position
wherein fluid is blocked from flowing therethrough to said timing
chamber; and
an electromagnetic fuel control valve positioned in said fuel
common rail for controlling the flow of fuel to said metering
chamber, said electromagnetic fuel control valve being movable
between an open position wherein fuel may flow therethrough to said
metering chamber and a closed position wherein fuel is blocked from
flowing therethrough to said metering chamber, wherein said
electromagnetic fuel control valve and said electromagnetic timing
fluid control valve are each movable from said closed position to
said open position and from said open position to said closed
position to define a fuel metering event and a timing fluid
metering event, respectively, during which a predetermined quantity
of fuel and timing fluid, respectively, are metered into said
metering chamber and said timing chamber, respectively.
23. The metering system of claim 22, wherein said plunger means is
operable to be placed in a fuel receiving mode establishing a
metering period during which fuel may flow through said metering
circuit into said metering chamber, said plunger means operable to
be placed in a timing fluid receiving mode establishing a timing
period during which timing fluid may flow through said timing fluid
common rail into said timing chamber, and said plunger means
operable to be placed in an injection mode in which fluid flow
through both said circuits to both of said chambers is blocked
thereby for producing injection of the fuel in said metering
chamber through said injection orifice.
24. The metering system of claim 23, wherein at least a portion of
said metering period of each of said one or more injectors occurs
during said timing period of the same injector.
25. The metering system of claim 24, wherein said plunger means is
operable to move through periodic injection strokes in which said
plunger means moves inwardly in said injector cavity toward the
said injection orifice for each cycle of the engine causing fuel to
be expelled from said injector cavity through said injection
orifice to the combustion chamber, said fuel metering event and
said timing fluid metering event occurring only between said
periodic injection strokes.
26. The metering system of claim 24, wherein said plunger means is
operable to move through a metering stroke in which said plunger
means moves outwardly in said injector cavity away from said
injection orifice, said fuel metering event and said timing fluid
metering event occurring only during said metering stroke.
27. The metering system of claim 22, wherein said fluid supply
means includes a fuel supply pump for supplying both fuel and a
timing fluid to said one or more injectors.
28. The metering system of claim 22, wherein said electromagnetic
timing fluid control valve is movable between an open position
wherein timing fluid may flow therethrough to said timing chamber
and a closed position wherein fluid is blocked from flowing
therethrough to said timing chamber to define a timing event during
which the timing fluid at a predetermined pressure forces said
plunger means toward said metering chamber for producing injection
of the fuel in said metering chamber through said injection
orifice.
29. The metering system of claim 22, wherein said fuel metering
circuit each includes a fuel supply port formed in said injector
body and a spring-loaded check valve positioned upstream of said
supply port for permitting fuel into said metering chamber during
said metering period and for preventing the flow of fuel from said
metering chamber during the period of injector operation when the
metered fuel is injected.
30. The metering system of claim 29, wherein said inner plunger
section reciprocates adjacent to said injection orifice and said
metering chamber is positioned adjacent said injection orifice.
31. The metering system of claim 27, wherein said fluid supply
means supplies timing fluid to said timing fluid common rail at a
substantially constant pressure and supplies fuel to said fuel
common rail at a substantially constant pressure.
32. The metering system of claim 27, wherein said fuel pump
includes a pressure regulator for varying the fuel supply pressure
based on engine operating conditions.
33. The metering system of claim 27, further including at least one
flow control valve positioned downstream of said fuel pump for
providing a fixed fuel flow rate independent of upstream and
downstream fuel pressures.
34. The metering system of claim 33, wherein said at least one flow
control valve includes two flow control valves, each of said two
flow control valves positioned adjacent one of said electromagnetic
valves.
35. The metering system of claim 22, wherein said timing fluid
common rail and said fluid timing circuit is fluidically separate
from said fuel common rail and said fuel metering circuit.
36. The metering system of claim 35, wherein said fluid supply
means includes a lube oil supply pump for supplying lube oil to
said timing fluid common rail and a fuel supply pump for supplying
fuel to said fuel common rail.
Description
TECHNICAL FIELD
BACKGROUND OF THE INVENTION
There is a continuing need for a simple, reliable, low cost yet
high performance fuel injection system which can effectively and
predictably control both fuel injection timing and metering.
However, the design of such a fuel injection system necessarily
involves acceptance of some characteristics which are less than
optimal since the basic goals of low cost, high performance and
reliability are often in direct conflict. For example,
distributor-type fuel injector systems having a single centralized
high pressure pump and a distributor valve for metering and timing
fuel flow from the pump to each of a plurality of injection
nozzles, such as disclosed in Japanese Application No. 57-68532
(Komatsu), are less expensive to construct than are other types of
injection systems. However, distribution-type systems are not as
reliable in operation as other types of systems due to
unpredictable/uncontrollable behavior of high pressure fluids
within the fluid line connecting the centralized high pressure fuel
pump to the individual injector nozzles.
Many of the drawbacks associated with distributor-type systems can
be overcome by providing an individual cam operated unit injector
at each engine cylinder location, such as illustrated in U.S. Pat.
No. 4,392,612, whereby only low pressure fuel needs to be supplied
to each injector, since the high pressure necessary for injection
can be supplied by the cam actuated pump located in each injector
immediately adjacent the engine cylinder. Each injector also
includes a control valve, e.g. solenoid valve, mounted on the
injector body to control the amount of fuel injected into each
cylinder. However, the requirement of an individual pump and
control valve for each injector creates substantially higher
manufacturing costs as compared with distributor-type systems. In
addition, the unit injectors disclosed in U.S. Pat. No. 4,392,612,
are designed so that each solenoid valve must close and open during
a single injection stroke of the injector pump or plunger as the
plunger moves inwardly to control the beginning and end of
injection, respectively. Since each injection stroke of the plunger
must occur in an extremely short period of time near the top dead
center position of the corresponding engine piston as it completes
the compression stroke and commences the power stroke, the design,
operation and control of the solenoid valve becomes a critical, and
often costly, consideration in the design of the unit fuel
injector. In fact, it has been found that these types of unit
injectors are not always capable of achieving predictable and
effective control of the timing and metering of fuel injection over
a wide range of operating conditions.
Commercially competitive fuel injector systems of the future will
almost certainly need some capacity for controlling the timing of
injection completely independent from the quantity in response to
changing engine conditions in order to achieve acceptable pollution
abatement and fuel efficiency. Certainly, some emission control
standards will be difficult or impossible to meet unless both
timing and quantity of fuel can be controlled extremely accurately
on a cycle-by-cycle basis depending on operator demand and engine
conditions. However, achieving the high degree of control required
in high pressure distributor-type systems will be extremely
difficult due to the high pressure waves transmitted through the
high pressure lines connecting the distributor pump with the
individual injectors. Likewise, although numerous attempts have
been made to design a unit injector system which provides for
variable timing and metering, a unit fuel injector system which is
both economical and highly accurate has not yet been achieved.
U.S. Pat. Nos. 4,281,792 and 4,531,672, provide examples of
attempts to solve this dilemma by disclosing unit fuel injectors
which attempt to achieve independent control over injection timing
and metering while minimizing the demands on the solenoid valve.
The unit injector disclosed in U.S. Pat. No. 4,281,792 includes a
two-part plunger having a variable volume hydraulic chamber
separating the plunger sections and a single solenoid valve which
commences the injection on the inward stroke of the plunger by
closing to form a hydraulic link between the plunger sections. The
point of closure can be varied to vary the point at which injection
commences as illustrated by points B,C and D of FIGS. 8 and 9 of
the '792 patent. Because points B,C and D are located on a
rotatively steep portion of the cam surface, the point of closure
of the control valve is quite time sensitive. On the outward
stroke, the solenoid valve opens at a selected point to control the
quantity of fuel metered for injection on the subsequent
downstroke. The point of opening is illustrated by point E which
may occur over a relatively less steeply sloped portion of the
curve and such opening is less time sensitive. Therefore, this
design eliminates the need for the solenoid to control both timing
and metering in the relatively short time period of the inward
stroke of the plunger. However, since the solenoid must still
operate during the inward stroke to control timing and the inward
stroke must occur over a relatively short time period (steep
portion of cam profile) within the total cycle time of the engine
piston, operating requirements for the solenoid and its associated
circuitry still remain high.
U.S. Pat. No. 4,531,672 further minimizes the operating
requirements of the solenoid valve by providing a unit injector
which operates only on the outward stroke of the plunger, or during
a dwell when the plunger is not moving, to control both timing and
metering. As a result, a greater period of time, or window of
opportunity, is provided within which the solenoid may operate.
However, this fuel system, like the one disclosed in U.S. Pat. No.
4,281,792, does not entirely separate the timing and metering
functions of each unit injector primarily because a single solenoid
and associated supply passage serves both the metering and timing
passages for each injector. As a result, the metering and timing
phases can not occur at the same time. Consequently, the window of
opportunity for metering corresponding to a single outward stroke
of the plunger must be allocated between the metering and timing
phases thereby undesirably decreasing the amount of time available
for the completion of each phase. Moreover, within a given window
of opportunity for metering, the single solenoid valve must be
accurately controlled to open and then close with respect to the
opening and closing of a supply or drain port by the plunger.
Unit injector systems such as those disclosed in U.S. Pat. Nos.
4,281,792 and 4,392,612 also suffer from the disadvantages inherent
in systems having individual solenoid valves associated with each
unit injector. Unlike a more conventional open nozzle unit
injector, for example as disclosed in FIG. 16 of U.S. Pat. No.
3,951,117, which operates on pressure/time principles to control
both metering and timing and therefore does not require a solenoid
valve, these solenoid operated unit injectors require a solenoid
valve for each injector resulting in a more complex and costly
injector. In addition, the injector barrel must be forged to
include a boss for receiving the solenoid valve body instead of
using the simpler screw machining process for producing a symmetric
injector body. Also, the boss and solenoid assembly extend into the
cylinder head adjacent the injector restricting the space available
for other engine components, such as the injector and valve drive
train assemblies, while increasing the overall size of the engine.
Lastly, many of these solenoid valves must be designed to withstand
the extremely high pressures of the timing or metering fluids under
compression by the injector plunger thus increasing the cost of the
injector.
As mentioned above, the open nozzle fuel injector, such as
disclosed in FIG. 16 of U.S. Pat. No. 3,951,117 and in FIG. 1 of
U.S. Pat. Nos. 4,971,016 and 5,042,445, avoids the need for a
solenoid valve since the amount of injection fuel and timing fluid
metered to the injector is controlled by pressure-time metering,
that is, the pressure of the fuel or fluid supplied to the injector
through a precisely dimensioned feed orifice and the time period
the plunger uncovers the feed orifice. However, this type of
pressure-time control requires the fuel pressure to be constantly
and accurately varied in response to changing engine conditions. To
achieve this goal, many of these systems include pressure
transducers in the supply lines to each injector for sensing the
fuel supply pressure and providing feedback to the pressure
controller thus adding to the overall cost of the fuel system.
Moreover, open nozzle pressure-time fuel injector systems do not
allow for individual cylinder control since fuel and timing fluid
is constantly fed to each injector through a pressure regulator. In
order to improve emissions and fuel economy, it is occasionally
desirable to prevent one or more selected cylinders from providing
power to the engine by stopping the injection of fuel into the
combustion chamber by the injector corresponding to the particular
cylinder or cylinders. However, this type of cylinder "cut out" is
not practical with open nozzle, pressure-time, common rail
injectors since a single injector cannot be easily isolated from
the other injectors during operation of the engine.
Another problem associated with open nozzle pressure-time injectors
is the inability of the injector to provide fast, positive response
to fuel supply pressure changes. The amount of fuel metered is
controlled at least in part by the fuel supply rail pressure which
is varied depending on various engine conditions. When the fuel
supply pressure is sharply decreased in response to changing engine
conditions, it takes a period of time for the fuel pressure in the
supply passage adjacent the injector to decrease to the new
pressure level. This delay in response impedes the ability of the
pressure-time metering control system to provide fast, accurate
control of timing and metering.
Another problem commonly experienced in open nozzle pressure-time
injectors is the presence of combustion gases in the supply passage
between the supply port and the inlet check valve. Gases from the
combustion chamber are pushed up into the supply passage by the
engine piston. These gases interfere with the control of fuel
metering and, therefore, must be removed. One attempt to remove the
gases includes forming a scavenging flow passage in the supply side
distinct from the supply or feed port for directing the gas
containing supply fuel through the injector to drain creating a
scavenging effect. However, such efforts to remove the gases have
not always been completely successful. Similarly, the combustion
gas or cylinder pressure may affect the amount of fuel metered in
another way. The supply fuel must be metered against the cylinder
pressure acting up through the metering chamber of the injector
even though no gas actually travels to the fuel supply. At the
relatively low fuel pressures necessary at low operating speeds and
loads for efficient operation of open nozzle pressure-time
injectors, the effects of cylinder pressure on fuel metering can be
substantial resulting in yet another variable which must be
considered before achieving accurate control of metering throughout
the range of operating conditions.
Other fuel injection systems have been developed in an attempt to
overcome some of the deficiencies discussed above while also
attempting to achieve efficiency of combustion, fuel economy and
emissions abatement. In order to achieve these goals, it is certain
that the fuel supply system must be able to provide precisely
controlled amounts of fuel and timing fluid to each injector at the
precise time required in the injection cycle. U.S. Pat. No.
4,621,605 provides an example of such an attempt by disclosing a
positive displacement fuel injection system which forms and
delivers pre-metered slugs of fuel and timing fluid to unit
injectors. This system is capable of varying the size of the fuel
and timing slugs on a cycle-by-cycle basis without the use of
individual solenoid valves and pressure-time metering. However, the
system uses a complex fuel pump including a piston/chamber
arrangement, variable position mechanical stop and a 3-way flow
control valve for each fuel metering and timing fluid circuit.
Consequently, the system is complicated, costly and impractical for
many purposes. Moreover, the slug forming chambers are remote from
each cylinder which adds line condition variables that are not
necessarily controllable or predictable. In addition, since only
one fuel metering and one timing control arrangement serve all
injectors of the engine, each control arrangement must deliver, in
the time period of a given engine cycle, a number of metered slugs
corresponding to the total number of injectors in the engine.
Therefore, the total time period of a complete cycle of the engine
must be allocated into a number windows of opportunity for metering
corresponding to the total number of injectors in the engine, e.g.
six windows for a six cylinder engine. As a result, the window of
opportunity for metering for each injector cannot be maximized in
the total engine cycle time period and the operating requirements,
e.g. response time, of the control arrangement must be very
high.
As previously discussed, U.S. Pat. No. 4,531,672 to Smith discloses
a unit fuel injector containing a fluid timing circuit and a fluid
metering circuit for providing fuel flow to respective timing and
metering chambers by means of a single solenoid valve which is
adapted to control separately timing and metering through variation
in the time of opening and closing, respectively, during each cycle
of operation. While this type of injector design may provide
adequate control over both timing and metering, it uses common
metering and timing passages thereby requiring engine fuel to be
used as the timing fluid..As a result, a greater amount of fuel is
supplied to the unit injector than is necessary to supply the
injection chamber since fuel is continually cycled through the
timing chamber during injector operation. This results in a
substantial amount of timing fuel being heated within the injector
and subsequently drained or spilled to the fuel supply tank. The
hot fuel returned to the supply tank causes undesired fuel
evaporation and often requires the installation of fuel cooling
heat exchangers to reduce the temperature of the fuel in the supply
tank.
The problems associated with draining excessive quantities of hot
fuel to the supply tank and the accompanying pressure spikes have
become even more apparent due to recent and upcoming legislation
placing strict emission standards on engine manufacturers resulting
from a concern to improve fuel economy and reduce emissions. In
order for new engines to meet these standards, it is necessary to
produce fuel injectors and systems capable of achieving higher
injection pressures, shorter injection durations and more accurate
control of injection timing. High injection pressures may be
achieved in a number of ways such as by varying the cam profile,
plunger diameter and/or number and size of injection orifices.
Various techniques have been developed to control timing including
mechanical, e.g. racks for rotating injector plungers having
helical control surfaces; electronic, e.g. valves for controlling
the start and/or end of injection and hydraulic, e.g. variable
length hydraulic links. With respect to the latter, timing is
advanced by introducing more timing fluid into the timing chamber
which effectively lengthens the fluid link between the injector
plungers. In the typical injector, as a result of this lengthened
link, the pumping plunger commences injection and/or reaches its
bottom most position at an earlier point in the rotation of the
corresponding cam. Accordingly, fuel injection can occur at a point
in the combustion cycle when the piston of the engine is still
moving upward.
Because fuel is normally used as the timing fluid in injectors of
this type, the amount of fuel which is supplied to and drained away
from the injector of an engine necessarily increases as compared
with injectors employing non-hydraulic timing control or no timing
control. The amount of heat absorbed by the fuel and ultimately the
temperature of the fuel in the fuel supply tank has been found to
increase to an unacceptably high level.
Other fuel injector and fuel injection system designs which provide
for variable timing and metering are disclosed in U.S. Pat. Nos.
4,249,499 to Perr and 4,410,138 to Peters et at. The unit injector
design disclosed in the '499 Perr patent includes a timing
mechanism having movable pistons connected between a cam drive and
an injector plunger that allow timing fluid to enter a timing
chamber to form a variable length hydraulic link between the
pistons depending on the pressure of the supply wherein the length
of the link determines the point at which injection is initiated.
The timing fluid circuit, which preferably uses engine lubricant,
is separate from the fuel supply or metering circuit. Therefore,
since lube oil is used as a timing fluid in a separate timing
circuit, the above-mentioned hot fuel drain problem is avoided in
this design. However, this design controls injector timing using a
variable pressure timing fluid mechanism, while fuel metering
control is based on pressure-time metering. Consequently, both
timing fluid pressure and metering fuel pressure are critical
variables which must be carefully controlled for proper timing and
metering. Precise control of fuel and fluid pressure to accurately
and effectively control both fuel injection timing and metering
over a wide range of operating conditions is often difficult to
achieve.
U.S. Pat. No. 4,410,138 to Peters et al. discloses a fuel injector
having infinitely variable timing using a two part injector plunger
which forms a variable link timing chamber between the upper and
lower plungers for receiving timing fluid. Here again, although the
timing fluid circuit is completely separate from the fuel metering
circuit, precise control of both the timing fluid pressure and
metering fuel pressure are necessary for accurate and reliable
control of timing and metering.
U.S. Pat. No. 5,143,291 to Grinsteiner discloses a unit fuel
injector using high pressure lubricating oil to pressurize the fuel
for injection. However, each fuel injector requires a separate
solenoid valve for controlling the flow of lubricating oil
resulting in a more complex and costly injector. Also, the
lubricating oil enters each injection at high pressure and is not
compressed in a timing chamber by an engine-operated timing
plunger. Therefore, the lubricating oil in each injector does not
experience temperature increases associated with the high
compression of timing fluid in injectors having mechanically driven
pump plungers.
Another important concern accentuated by higher injection pressures
is the need to adequately cool unit injectors during operation. In
the fuel injector design disclosed in U.S. Pat. No. 4,531,672 to
Smith, both the metering fuel and the timing fuel inherently
function to cool the unit injector. However, it has been discovered
that when fuel is used as the timing fluid, excessive heat may be
absorbed by the fuel resulting in the fuel assuming an unacceptably
high temperature over extended periods of engine operation. Thus,
in order to ensure adequate cooling of the injector, the fuel in
the fuel supply tank must be cooled using expensive coolers.
Another important requirement of fuel injectors using engine fuel
as timing fluid is to provide a leak off passage between the
uppermost plunger and the rocker arm or driving assembly. Without
such a leak off passage, fuel leakage by the uppermost plunger
would cause the fuel to be mixed with the engine lubrication oil
supplied to the rocker arm and linkage assembly impairing the
lubrication qualities of the lube oil and ultimately increasing
engine wear.
Consequently, there is a need for a simple, reliable, low cost yet
high performance fuel injection system which can effectively and
predictably control both fuel injection timing and metering by
maximizing the time period available for metering of fuel and
timing fluid. There is also a need for such a fuel injection system
which can effectively and predictably control both fuel injection
timing and metering while adequately cooling the injector internals
without causing excessive heating of the engine fuel.
SUMMARY OF THE INVENTION
It is an object of the invention, therefore, to overcome the
disadvantages of the prior art and to provide an injection fuel and
timing fluid metering system capable of effectively and predictably
controlling both fuel injection timing and metering.
It is another object of the present invention to provide a metering
system which minimizes the number of control valves used to control
metering while providing a greater time period, for each injector,
during which timing fluid and injection fuel metering may
occur.
It is yet another object of the present invention to provide a
metering system which minimizes the operating requirements of the
control valves used in the metering system.
It is a further object of the present invention to provide a
metering system which permits timing fluid metering and injection
fuel metering to occur simultaneously.
It is a still further object of the present invention is to provide
a metering system which eliminates the need for the control valves
to operate to control metering during the relatively short timing
period of the inward stroke of the injector plunger.
Still another object of the present invention is to provide a
metering system which does not require the control valves to be
accurately controlled to open and close with respect to the opening
and closing of a supply or drain port by the plunger.
Yet another object of the present invention is to provide a
metering system which eliminates the need for a control valve for
each injector while still providing individual cylinder control and
cutout.
A still further object of the present invention is to provide a
metering system which decreases the sensitivity of the metering
system on the fluid supply pressure while providing fast, positive
response to fuel supply pressure changes.
It is yet another object of the present invention is to provide a
metering system which eliminates the need for a scavenging flow
passage in each injector to remove combustion gas the supply
fuel.
It is a further object of the present invention to provide a
metering system which minimizes the effects of cylinder pressure on
fuel metering.
It is another object of the present invention to provide a fuel
injection system using lubrication oil as timing fluid to
effectively cool and lubricate the fuel injectors without causing
excessive heating of the engine's fuel.
It is yet another object of the present invention to provide a fuel
injection system which minimizes both the amount of fuel required
by the injectors and the amount of heated fuel returned to the fuel
supply tank from the injectors.
These and other objects are achieved by providing a metering system
for controlling the amount of fuel supplied to the combustion
chambers of a multi-cylinder internal combustion engine comprising
a fuel pump for supplying fuel at low pressure to a first and a
second group of unit fuel injectors via first and second fuel
supply paths, respectively. A first solenoid-operated fuel control
valve positioned in the first fuel supply path between the fuel
pump and the first set of injectors controls the flow of fuel to
the first set of injectors while a second solenoid-operated fuel
control valve positioned in the second fuel supply path between the
fuel pump and the second set of injectors controls the flow of fuel
to the second set of injectors. Only one injector from the first
group and one injector from the second group of injectors can be
placed in a mode for receiving fuel from the fuel pump at any given
time during the operation of the engine thereby allowing the
metering of each injector to be independently controlled over a
greater time period. The system may also include a first
solenoid-operated timing fluid control valve positioned in a first
timing fluid supply path associated with the first group of
injectors and second solenoid-operated timing fluid control valve
positioned in a second timing fluid supply path associated with the
second group of injectors wherein at any given time only one
injector from the first group and one injector from the second
group of injectors can be placed in a timing fluid receiving mode.
The injectors are capable of being in the fuel receiving mode,
establishing a metering period, and the timing receiving mode,
establishing a timing period, at the same time to increase the
amount of time available for metering both timing fluid and fuel.
By grouping the various injectors based on the order of injection
so that the injectors from each group are placed in the injection
mode in spaced periods throughout each cycle of the engine, e.g.
injectors from other groups injecting in the period of time between
each injection mode, the system can be designed to permit longer
metering and timing periods.
The unit injectors may include an injector body having an injection
orifice at one end and a cavity communicating with the orifice and
containing inner and outer plunger sections arranged to form a
variable volume metering chamber between the inner plunger and the
orifice for receiving fuel during the metering period and a
variable volume timing chamber between the inner and outer plungers
for receiving timing fluid during the timing period. The
solenoid-operated valves are moved between open and closed
positions during the metering and timing periods to allow fuel and
timing fluid, respectively, to flow to the metering and timing
chambers thereby defining metering and timing events, respectively.
The metering and timing events for each injector occur only between
periodic, relatively quick injection strokes of the plungers
.thereby minimizing the operating response time requirements of the
control valves. The fuel supply passage to the metering chamber of
each injector contains a spring-loaded check valve for preventing
the flow of fuel out of the metering chamber while also preventing
combustion gases from entering the supply passage and disturbing
the effective control of metering. The injectors may be either open
or closed nozzle injectors. A pressure regulator maintains the
pressure in the timing fluid and fuel supply paths at a
substantially constant pressure. Also, flow control valves may be
provided downstream of the fuel pump to provide a fixed flow rate
independent of fuel pressures upstream and downstream of the flow
control valves.
The plungers of the injectors may be reciprocated by a cam driven
by the engine. Alternatively, a hydraulic intensification system
may be used by providing a timing fluid control valve for each
injector which provides very high pressure timing fluid to a timing
chamber positioned adjacent the plunger to permit the pressure of
the timing fluid acting on the plunger to force the plunger
inwardly causing injection of the fuel in the metering chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of the preferred embodiment of the
individual timing and fuel injection metering system of the present
invention;
FIG. 2 is a cross-sectional view of a closed nozzle unit injector
used in the metering system of FIG. 1 showing the plungers of the
injector in their respective innermost positions prior to being
placed in a fuel receiving mode;
FIG. 3A is a cross-sectional schematic view portion of the metering
system of FIG. 1 showing a first set of unit injectors with a pair
of fuel injection and timing fluid control valves and associated
supply passages showing the plunger positions of the respective
unit injectors with the engine crank angle at 0.degree.;
FIG. 3B is a cross-sectional schematic of the FIG. 3A metering
system showing the plunger positions of the respective unit
injectors with the engine crank angle at 80.degree.;
FIG. 3C is a cross-sectional schematic of the FIG. 3A metering
system showing the plunger positions of the respective unit
injectors with the engine crank angle at 160.degree.;
FIG. 3D is a cross-sectional schematic of the FIG. 3A metering
system showing the plunger positions of the respective unit
injectors with the engine crank angle at 240.degree.;
FIG. 4 is a graph showing the metering and injection periods of
each injector of the FIG. 1 metering system throughout a complete
cycle of the engine;
FIG. 5 is a cross-sectional view of an alternative embodiment of a
unit injector which may be used in the metering system of FIG. 1
showing an open nozzle unit injector in a fuel receiving mode;
FIG. 6 is a second embodiment of the present invention including a
flow control valve associated with each injection fuel and timing
fluid control valve;
FIG. 7 is a third embodiment of the present invention including a
pressure regulator positioned in a bypass circuit;
FIG. 8 is a fourth embodiment of the present invention including a
separate timing control valve for each injector, a high pressure
reservoir and a high pressure pump for supplying high pressure
timing fluid to the injectors; and
FIG. 9 is a fifth embodiment of the present invention which uses
lube oil as the timing fluid supplied through timing fluid supply
paths which are fluidically separate from the fuel metering supply
paths.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Throughout this application, the words "inward", "innermost",
"outward" and "outermost" will correspond to the directions,
respectfully, toward and away from the point at which fuel from an
injector is actually injected into the combustion chamber of an
engine. The words "upper" and "lower" will refer to the portions of
the injector assembly which are, respectively, farthest away and
closest to the engine cylinder when the injector is operatively
mounted on the engine.
Referring to FIG. 1, there is shown a timing fluid and injection
fuel metering system 10 of the present invention as applied to a
six-cylinder 5 engine (not shown) having one injector associated
with each cylinder. Generally, the metering system 10 includes a
fuel supply pump 12 for supplying low pressure fuel both to a first
set of unit fuel injectors 14 via a timing fluid control valve 18
and an injection fuel control valve 20 and to a second set of unit
fuel injectors 16 via a timing fluid control valve 22 and an
injection fuel control valve 24. Each fuel injector 26 of each set
of injectors 14, 16 is operable to create a timing period and a
metering period within which the control valves 18, 20, 22, 24
operate to define the amount of timing fluid and injection fuel,
respectively, metered to the injector. By providing separate timing
and metering circuits controlled individually by a respective
control valve, the metering system can effectively and predictably
control both fuel injection timing and metering at the same time
during the metering stroke of the injector plunger thereby
maximizing the time period or window of opportunity available for
metering of fuel and timing fluid. Moreover, the metering system
maximizes the time period for metering for each injector of a
particular set of injectors by selectively grouping the injectors
with respect to the sequence of injection periods of the entire
bank of injectors to allow the metering and timing periods of a
specific group to be spread throughout the total cycle time of the
engine.
Fuel supply pump 12 is a gear pump which draws fuel from a
reservoir 28 and directs it to a common supply passage 30. Supply
passage 30 supplies fuel to both a first fuel supply path 32 and a
second fuel supply path 34 providing fuel for injection to the
first and second set of injectors 14, 16 respectively. Supply
passage 30 also supplies fuel to both a first timing fluid supply
path 33 and a second timing fluid supply path 35 providing fuel, as
timing fluid, to the first and second set of injectors 14, 16
respectively. A bypass valve 36 positioned in a bypass line of
supply pump 12 maintains the fuel supply at a substantially
constant pressure which is preferably between 100 and 500 psi.
Bypass valve 36 is spring biased to open at a predetermined
downstream fuel pressure to allow fuel from the outlet side of pump
12 to flow through the bypass line to the inlet side of pump 12
thereby maintaining the supply fuel pressure at the predetermined
level.
The timing fluid control valves 18, 22 and injection fuel control
valves 20, 24 are positioned in the respective timing fluid supply
paths 33, 35 and fuel supply paths 32, 34 to control the flow of
timing fluid and injection fuel to the respective injectors. The
control valves 18, 20, 22, 24 are each of the electromagnetic or
solenoid-operated type valve assemblies having valve elements
operable between open and closed positions to control the flow of
timing fluid and fuel from the supply paths 32, 33, 34, 35 to the
injectors. The control valves 18, 20, 22, 24 are controlled by an
electronic control unit (ECU) 38 which receives signals such as
engine speed and position, accelerator pedal position, coolant
temperature, manifold pressure and intake air temperature signals
from corresponding engine sensors indicated generally at 40. On the
basis of these signals, the ECU 38 judges the engine operating
condition and emits control signals to the control valves 18, 20,
22, 24 such that the fuel injection timing and the amount of fuel
to be injected through each injector 26 are optimized for the
engine operating condition.
First timing fluid control valve 18 and second timing fluid control
valve 22 deliver fuel into respective timing fluid common rail
portions 42, 44 of the respective first and second timing fluid
supply paths 33, 35. Likewise, first and second injection fuel
control valves 20, 24 control the flow of fuel to respective first
and second injection fuel common rail portions 46, 48 of the
respective first and second fuel supply paths 32, 34. Each injector
26 includes a timing circuit 50 for receiving timing fluid from
timing fluid common rail 42, 44 and a metering circuit 52 for
directing fuel from common rail portions 46, 48 into the injector
for subsequent injection into the corresponding cylinder of the
engine.
The types of injectors which may be used in the present timing
fluid and fuel metering system will now be described in detail.
Referring to FIG. 2, there is shown a closed nozzle unit fuel
injector 36 which includes an injector body 54 formed from an outer
barrel 56, a spacer 58, a spring housing 60, a nozzle housing 62
and a retainer 64. The spacer 58, spring housing 60 and nozzle
housing 62 are held in a compressive abutting relationship in the
interior of retainer 64 by outer barrel 56. The outer end of
retainer 64 contains internal threads for engaging corresponding
external threads on the lower end of outer barrel 56 to permit the
entire unit injector body 54 to be held together by simple relative
rotation of retainer 64 with respect to outer barrel 56.
Outer barrel 56 includes a plunger cavity 66 which opens into a
larger upper cavity 68 formed in an upper extension 70 of outer
barrel 56. A coupling 72 is slidably mounted in upper cavity 68 and
includes a cavity 73 for receiving a link 75. Coupling 72 and link
74 provide a reciprocable connection between the injector and a
driving cam (not shown) of the engine. A coupling spring 74 is
positioned around extension 72 to provide an upward bias against
coupling 72 to force link 75 against the injector drive train and
corresponding cam (not shown). The drive train may include a rocker
assembly for connecting link 75 to the cam.
Plunger cavity 66 extends longitudinally through outer barrel 56
for receiving both an outer timing plunger 76 and an inner metering
plunger 78. Timing plunger 76 includes an upper portion 80 having
an outer diameter which permits upper portion 80 to slidably engage
plunger cavity 66 while substantially preventing fuel leakage
between upper portion 80 and plunger cavity 66. Any fuel leaking by
upper portion 80 is collected in an annular groove 83 and directed
into a drain passage 85 communicating with groove 83. A lower
portion 82 formed on the inner end of upper portion 80 extends
inwardly towards spacer 58. Lower portion 82 has a smaller diameter
than plunger cavity 66 and upper portion 80 to form an annular
cavity 84. The outermost end of timing plunger 76 contacts the
innermost end of link 73 to cause timing plunger 76 to move in
response to cam rotation. The innermost end of inner portion 82 of
timing plunger 76 together with the outermost end of metering
plunger 78 forms a timing chamber 86 for receiving timing fluid
from the particular timing fluid control valve 18, 22 associated
with the set of injectors to which the injector belongs.
Timing circuit 50 provides both a delivery and a spill path for the
timing fluid during each injection cycle. Timing circuit 50
includes a branch passage 88 (shown in FIG. 1), timing chamber 86
and various supply and spill passages which will now be described
in greater detail. Timing fluid is provided to timing chamber 86
from timing fluid common rail portion 42 by branch passage 88 and a
supply port 90 formed in outer barrel 56 and extending radially
from timing chamber 86. A spring biased inlet ball check valve 92
positioned in supply port 90 prevents timing fluid from flowing
from timing chamber 86 through supply port 90 while allowing timing
fluid to pass into timing chamber 86.
Outer barrel 56 includes a timing spill orifice 94 and a timing
spill port 96 extending radially from cavity 66. Timing spill
orifice 94 and spill port 96 provide communication between timing
chamber 86 and annular timing fluid spill channel 98 formed between
outer barrel 56 and retainer 64. Timing fluid drain ports 100 are
provided in retainer 64 adjacent annular channel 98 to allow timing
fluid to flow from annular channel 98 to a timing fluid drain
system which is fluidly connected with that portion of the injector
cavity (not illustrated) formed in the cylinder head of the engine
adjacent timing fluid drain ports 100.
Fuel metering circuit 52 is formed to provide both a delivery and
spill path for the metering fuel during each cycle of the engine.
Fuel metering circuit 52 includes a metering chamber 102 and
various supply and spill passages which will now be described in
greater detail. As shown in FIG. 2, metering chamber 102 is formed
between the innermost end of metering plunger 78 and spacer 58.
Metering chamber 102 receives fuel from a fuel supply port 104
formed in retainer 64 which communicates with a branch passage 106
(shown in FIG. 1 ). Fuel flows through supply port 104 into an
annular channel 108 formed between the lower portion of outer
barrel 56 and retainer 64. Annular channel 108 continues inwardly
between spacer 58 and retainer 64 to connect with a radial passage
formed in the upper surface of spring housing 60. An inlet passage
112 extends through spacer 58 connecting radial passage 110 with
metering chamber 102. A spring loaded ball check valve 114
positioned in fuel inlet passage 112 permits passage of fuel at a
predetermined pressure from fuel supply port 104 to metering
chamber 102 while preventing fuel flow from metering chamber 102
through fuel inlet passage 112. A metering spill orifice 116 and
metering spill port 118 formed in the lower end of outer barrel 56
extend radially from cavity 66 adjacent metering plunger 78 to
communicate with annular channel 108. Metering plunger 78 includes
an annular groove 120, a radial passage 122 and an axial passage
124 in communication with each other to permit fuel to flow from
the metering chamber 102 to metering spill orifice 116 and spill
port 118 depending on the position of metering plunger 78 during
the operation of the injector as discussed in more detail
hereinbelow.
Spacer 58 also includes a fuel transfer passage 126 fluidically
communicating metering chamber 102 with a fuel passage 128 formed
in spring housing 60. Nozzle housing 62 includes a fuel passage 130
for directing fuel from passage 128 to a nozzle cavity 132 formed
in nozzle housing 62. As illustrated in FIG. 2, nozzle housing 62
also includes injector orifices 134 which are normally closed by an
axially slidable pressure actuated tip valve element 136 mounted in
nozzle cavity 132. A spring 138 positioned in a central bore 140
formed in spring housing 60 biases tip valve element 136 into the
closed position blocking injector orifices 134. When the pressure
of fuel within nozzle cavity 132 exceeds a predetermined level, tip
valve element 136 moves outwardly against the biasing force of
spring 138 to allow fuel to pass through the injector orifices 134
into the combustion chamber (not shown).
The operation of closed nozzle fuel injector 36 will now be
described with reference to FIGS. 1, 2 and 3A-3D. FIGS. 3A-3D
illustrate the sequential operation of only the first set of unit
fuel injectors 14 and control valves 18, 20. Also, FIGS. 3A-3D
illustrate the closed nozzle fuel injector 36 of FIG. 2 in a more
conceptual manner for ease of illustration and understanding of the
operation of the entire system. Each injector will be referred to
with the number corresponding to the cylinder to which it is
associated. The plunger position of closed nozzle fuel injector 36
as shown in FIG. 2 corresponds to the plunger position of injector
3 of FIG. 3A. In FIGS. 3A-3D, timing plunger 76 of each of the
respective injectors is operatively connected to a cam 142 via a
roller 144 instead of link 75 of FIG. 2. When roller 144 or link 75
is positioned against the outer base circle of cam 142 as
illustrated by injector 3 in FIG. 3A, timing plunger 76 and
metering plunger 78 are positioned in their respective innermost
positions or at bottom dead center. In this position, timing
chamber 86 is in its shortest possible form since lower portion 82
of timing plunger 76 abuts metering plunger 78. Metering plunger 78
is positioned to uncover timing spill orifice 94 and spill port 96
allowing timing fluid to drain from timing chamber 86. Also, radial
passage 122 and annular groove 120 are positioned to communicate
with metering spill orifice 116 and spill port 118 allowing fuel to
spill from axial passage 124, transfer passage 126, passage 128,
passage 130 and cavity 132 into annular channel 108. The entire
time roller 144 moves along the outer base circle of cam 142,
plungers 76, 78 are in the innermost position and, therefore, no
timing fluid and no fuel can be effectively metered into the timing
chamber 86 and metering chamber 102, respectively. As shown in FIG.
3B, once cam 142 rotates to allow roller 144 to move onto a ramp
portion 146, coupling spring 74 forces roller 144 and timing
plunger 76 outwardly as dictated by the profile of ramp portion 146
of cam 144. The movement of plunger 76 outwardly marks the
beginning of a timing period and a metering period during which
timing fluid control valve 18 and injection fuel control valve 20
may be operated to meter timing fluid and injection fuel into the
respective chambers. As shown in FIG. 3B, timing fluid control
valve 18 is operated to an open position by a signal from ECU 38
based on engine operating conditions to allow fuel to enter timing
chamber 86 via common rail portion 42, timing circuit 50, supply
port 90 and check valve 92 thus beginning a timing fluid metering
event. Injection fuel control valve 20 is also operated to an open
position by a signal from ECU 38 to allow fuel to flow from supply
path 32 into common rail portion 46 for delivery to metering
chamber 102 via metering circuit 52 thus beginning a fuel metering
event. Specifically, injection fuel flows into fuel supply port 104
and annular channel 108, through radial passage 110 and upwardly
into supply passage 112. Fuel is maintained at a pressure high
enough to overcome the spring pressure of check valve 114 thereby
allowing fuel to flow through supply passage 112 into metering
chamber 102. The pressure of the injection fuel entering metering
chamber 102 forces metering plunger 78 outwardly toward timing
chamber 86 closing off timing spill orifice 94 and metering spill
orifice 116. Once the proper amount of injection fuel is metered
into metering chamber 102 as dictated by engine operating
conditions, ECU 38 delivers a signal closing injection fuel control
valve 20 thus ending the fuel metering event and stopping the
outward movement of metering plunger 78 as shown in FIG. 3C. At
some point while the timing plunger 76 continues to move
outwardly,.ECU 38 will deliver a closing signal to timing fluid
control valve 18 causing valve 18 to move to a closed position
stopping the flow of timing fluid to timing circuit 50 thereby
ending the timing fluid metering event as shown in FIG. 3D.
Termination of the outward movement of timing plunger 76 as
determined by the profile of cam 144, marks the end of both the
timing and metering periods. As cam 144 of injector 3 continues to
rotate, ramped portion 146 forces timing plunger 76 inwardly
through an injection stroke placing unit injector 36 in an
injection mode in which fluid flow from supply paths 33, 32 through
both timing circuit 50 and metering circuit 52 to respective timing
and metering chambers 86, 102 is blocked by valves 18, 20 for
producing the injection of fuel in metering chamber 102 through
injection orifice 134. As timing plunger 76 moves inwardly, a
timing fluid link 148 is formed between timing plunger 76 and
metering plunger 78 in order to advance or retard the timing of
fuel injection. The length of fluid link 148 and, therefore, the
degree of advancement or retardation of injection timing, is
controlled by the mount of timing fluid permitted to enter timing
chamber 86 during the timing period. Since the pressure of the
timing fluid is maintained at a substantially constant level, the
amount of timing fluid metered to timing chamber 86 is primarily
dependent on the length of the timing fluid metering event which is
defined by the amount of time the timing fluid control valve 18 is
held in the open position during the timing period. Likewise, the
amount of injection fuel metered into metering chamber 102 is
primarily dependent on the length of the injection fuel metering
event which is defined by the amount of time the injection fuel
control valve 20 remains in the open position during the metering
period. Timing plunger 76 and fluid link 148 formed in timing
chamber 86 force metering plunger 78 downwardly forcing fuel from
metering chamber 102 into nozzle cavity 132 via transfer passage
126, fuel passage 128 and passage 130. When the pressure of fuel
within nozzle cavity 132 exceeds a predetermined level tip valve
element 136 moves outwardly to allow fuel to pass through the
injector orifices 134 into the combustion chamber (not shown). When
metering plunger 78 reaches its innermost position, annular groove
120 aligns with metering spill orifice 116 allowing fuel to spill
from metering chamber 102 through axial passage 124 and radial
passage 122 and back to the fuel supply via spill port 118. As a
result, the fuel pressure in nozzle cavity 132 is also relieved via
passages 126, 128, 130. When the fuel pressure in nozzle cavity 132
decreases to a level below the bias pressure of spring 138, spring
138 causes tip valve element 136 to move inwardly to close injector
orifices 134 thus terminating injection.
By providing separate timing and metering circuits, controlled
individually by a respective control valve, the metering system of
the present invention can effectively and predictably control both
fuel injection timing and metering at the same time during the
metering, or outward, stroke of timing plunger 76 and metering
plunger 78. In this manner, the period of time equal to the outward
stroke of the plungers, which is defined by the cam profile, need
not be divided into a metering period and a distinct separate
timing period since both timing and metering may take place
simultaneously. Therefore, by providing separate and distinct
timing and metering circuits and respective control valves, the
present invention maximizes the time periods available for both
injection fuel metering and timing fluid metering for each
injector.
Moreover, the metering system of the present invention maximizes
the time periods for metering timing fluid and fuel to each
injector of a particular set of injectors by selectively grouping
the injectors based on the order of the injection periods of the
entire bank of injectors to allow the metering periods of a
specific group to be spread throughout the total cycle time of the
engine. As shown in FIGS. 3A-3D and FIG. 4, in a six-cylinder
engine having one fuel injector for each cylinder, each unit fuel
injector will inject fuel one time during a given engine cycle. In
a conventional four-stroke diesel engine, each injector will inject
fuel one time during two rotations of the crankshaft which equal
720.degree. crank angle. As illustrated in FIG. 4, the injection
events of injectors 1-6, corresponding to cylinders 1-6, occur in a
specific sequential order throughout the 720.degree. cycle of the
engine. As previously mentioned, it is desirable to maximize the
time period available for metering timing fluid and injection fuel
into the appropriate chambers in order to increase the
predictability and control of fuel injection throughout the
engine's operating conditions. However, where only one control
valve is used to control the metering of fluid to all six
injectors, the metering periods cannot occur at the same time since
the control valve must complete metering to each injector before
operating to control metering to another injector. Therefore, the
total engine cycle time period must be divided into six distinct
separate metering periods. Referring to FIG. 4, in the present
invention, the injectors are selectively arranged into two
separately controlled sets of injectors such that the injection
period of each injector of a specific set is followed by the
injection period of an injector from a different set. Specifically,
injectors 1, 2 and 3 are grouped into a first set of injectors 14
served by timing fluid control valve 18 and injection fuel control
valve 20. Injectors 4, 5 and 6 are grouped into second set of unit
injectors 16 served by control valves 22, 24. Since each set of
injectors includes only three injectors instead of six, the total
engine cycle time corresponding to 720.degree. crank angle
associated with each set is only divided into three metering
periods. Moreover, the injectors are specifically arranged into
sets 14, 16 according to the sequence of injection periods, which
is 1, 5, 3, 6, 2 and 4, such that the injection periods alternate
between the sets throughout the engine cycle. Therefore, the
injectors from each group are placed in the injection mode in
spaced periods throughout each cycle of the engine, e.g. injectors
from other groups injecting in the period of time between each
injection mode. As a result, each of the three metering and timing
periods, associated with the three injectors of a given set, can be
significantly increased by providing the appropriate cam profile.
As shown in FIG. 4, the metering and timing periods associated with
each set 14, 16 are extended throughout substantially the entire
cycle time of the engine thereby maximizing the metering period of
each injector while minimizing the operating demands on control
valves 18, 20, 22, 24. Specifically, the metering and timing
periods of each injector extend for a period of time corresponding
to approximately 200.degree. crank angle.
Although the metering periods of injectors from different sets
occur at the same time, the metering periods of the injectors from
a given set of injectors must occur throughout separate, distinct
time intervals to allow the control valves to accurately deliver
the proper amount of timing fluid and fuel to only one injector at
any given time. Therefore, as shown in FIGS. 3A-3D and 4, each
injector of first set 14 is operated by cam 142 such that, at any
time during a given engine cycle, or in other words at any given
crank angle of the engine, only one injector of first set 14 is
positioned in a fuel receiving mode and a timing fluid receiving
mode for receiving fuel from injection fuel control valve 20 and
timing fluid control valve 18, respectively. Likewise, at any given
time during the engine cycle, only one injector from second set 16
is positioned in a fuel receiving mode and a timing fluid receiving
mode for receiving fuel from control valves 24, 22 respectively. As
shown in FIG. 3A, injector 3 is just beginning to be placed in the
timing fluid receiving mode and the injection fuel receiving mode
which establish a timing period and a metering period respectively.
Referring to FIG. 3B, when the control valves 18, 20 are opened to
begin the timing and metering events for injector 3, injectors 1
and 2 are incapable of receiving timing fluid and fuel from common
rail portions 42, 46. As shown in FIG. 3D, once control valves 18,
20 are closed and injector 3 is placed in the injection mode by cam
142, roller 144 and the plungers of injector 2 begin moving
outwardly placing injector 2 in a fuel receiving mode thus
beginning the metering period and timing period within which a fuel
metering event and timing fluid metering event may occur,
respectively. Meanwhile, injectors 1 and 3 are incapable of
receiving timing fluid and fuel from common rail portions 42, 46.
It should be understood that the second set of injectors 16 are
being similarly operated by respective cams such that the metering
periods of injectors 4, 5 and 6 are spread throughout substantially
the entire cycle time of the engine without overlapping. Also, as
can be seen from FIG. 4, the metering period of one injector from a
given set of injectors may overlap with the injection period of a
different injector from the same set of injectors since metered
fuel and timing fluid has a significantly lower pressure than the
timing fluid and injection fuel in the respective chambers during
the injection stroke of the plungers.
In an alternative embodiment of the present invention, as shown in
FIG. 5, an open nozzle fuel injector may be used instead of the
closed nozzle injector of FIG. 2. The open nozzle injector,
indicated generally at 150, includes an injector body 152 formed
from an outer barrel 154, an inner barrel 156, an injector cup 158
and a retainer 160. The inner barrel 156 and injector cup 158 are
held in a compressive abutting relationship in the interior of
retainer 160 by outer barrel 154. The outer end of retainer 160
contains internal threads for engaging corresponding external
threads on the lower end of outer barrel 154 to permit the entire
unit injector body 152 to be held together by simple relative
rotation of retainer 160 with respect to outer barrel 154.
Outer barrel 154 includes a plunger cavity 162 which opens into a
larger upper cavity 164 formed in an upper extension 166 of outer
barrel 154. A coupling 167 is slidably mounted in upper cavity 164
and includes a cavity 168 for receiving a link 170. Coupling 167
and link 170 provide a reciprocable connection between the injector
plungers and a driving cam (not shown) of the engine. A coupling
spring 172 is positioned around extension 166 to provide an upward
bias against coupling 167 to force link 170 against the injector
drive train and corresponding cam (not shown).
Fuel injector 150 includes a timing plunger 174, intermediate
plunger 176 and a metering plunger 178. Timing plunger 174 is
positioned for reciprocable movement in plunger cavity 162 so as to
abut the inner end of coupling 167. Intermediate plunger 176 is
positioned for reciprocable movement in plunger cavity 162 between
timing plunger 174 and metering plunger 178. The innermost end of
timing plunger 174 together with the outermost end of intermediate
plunger 176 forms a timing chamber 180 for receiving timing fluid
from the particular timing fluid control valve associated with the
set of injectors to which the injector belongs. Timing plunger 174
includes an axial passage 182 communicating with timing chamber 180
and extending outwardly to connect with a pair of diametrically
extending passages 184 spaced longitudinally along axial passage
182 in timing plunger 174. A spring biased inlet check valve 186
positioned in axial passage 182 inwardly of passages 184 prevents
the flow of timing fluid from timing chamber 180 through axial
passage 182 and passages 184. Outer barrel 154 includes a timing
fluid supply port 188 extending radially from plunger cavity 162
for supplying timing fluid to timing chamber 180. Outer barrel 154
also includes an annular recess 190 formed in the inner wall of
outer barrel 154 between timing plunger 174 and supply port 188.
Annular recess 190 extends axially along plunger cavity 162 a
sufficient distance to insure that at least one of passages 184
communicate with annular recess 190 and, therefore, supply port 188
at all times during plunger movement.
Intermediate plunger 176 includes an axial passage 192
communicating with timing chamber 180 and extending to communicate
with a radial passage 194. An annular groove 196 formed in
intermediate plunger 176 communicates with radial passage 194.
Outer barrel 154 includes a timing fluid spill orifice 198 and
spill port 200 extending radially from plunger cavity 162 to an
annular chamber 202 formed between outer barrel 154 and retainer
160. An annular spill ring 204 positioned around outer barrel 154
covers the opening of port 200 into chamber 202 and flexes radially
outwardly at a predetermined pressure to allow timing fluid to
spill from port 200 into chamber 202. A pair of drain ports 206
formed in retainer 160 adjacent annular chamber 202 directs timing
fluid spilled into chamber 202 to drain. An annular spacer 208
positioned around the lower end of outer barrel 154 is used to
position spill ring 204 in place over spill port 200. A drain
passage 203 formed in outer barrel 154 extends radially outwardly
from plunger cavity 162 adjacent timing chamber 180 to communicate
with an annular groove 205 formed by the upper end of retainer 160
and an annular flange 207 formed on outer barrel 154. A circular
ring valve 209 positioned in annular groove 205 around outer barrel
154 covers passage 203 preventing timing fluid flow from timing
chamber 180 until a predetermined pressure is reached. The ring
valve 209 flexes to open passage 203 during the injection event
under certain engine conditions, such as low speed operation to
limit the fluid pressure in timing chamber 180 and thus the peak
injection pressure. The design and function of spill valve 204 and
ring valve 209 are described in more detail in commonly owned U.S.
application Ser. No. 898,818 which is hereby incorporated by
reference.
Inner barrel 156 is generally cylindrically shaped to form a cavity
210 for receiving metering plunger 178. Inner barrel 156 includes a
lower wall 212 having a central aperture 214 which allows metering
plunger 178 to extend through cavity 210 inwardly into a bore 216
formed in injector cup 158. The outermost end of metering plunger
178 is positioned to contact free floating intermediate plunger 176
and includes a diametrically-extending hole 218 for receiving a
cross pin 220. Cross pin 220 engages an outer spring keeper 222 to
secure keeper 222 to the outermost end of metering plunger 178. An
inner spring keeper 224 positioned inside cavity 210 includes an
annular step 226 for abutment by an annular land 228 formed on
metering plunger 178. A spring 230 is positioned in cavity 210
between outer spring keeper 222 and inner spring keeper 224 so as
to bias outer spring keeper 222 into abutment with outer barrel 154
while also biasing metering plunger 178 outwardly.
A metering chamber 232 is formed in injector cup 158 between bore
216 and metering plunger 178. Fuel is supplied to metering chamber
232 via a fuel supply port 234 and supply orifice 236 formed in
retainer 160 adjacent inner barrel 156. An annular channel 238
formed between inner barrel 156 and retainer 160 directs fuel from
supply orifice 236 into an axially extending passage 239 formed
between injector cup 158 and retainer 160. A radial supply passage
240 formed in injector cup 158 extends radially inward from passage
239 to communicate with the lower end of a longitudinal cavity 241
formed in injector cup 158 adjacent bore 216. A radial supply
orifice 242 formed outwardly of passage 240 connects cavity 241 to
bore 216. A spring loaded fueling check valve 243, positioned in
longitudinal cavity 241 allows fuel above a predetermined pressure
to flow from passage 240 through passage 242 into metering chamber
232. Check valve 243 also prevents combustion gas from entering
supply passage 240 and interfering with the control of fuel
metering. Moreover, at low operating speeds and loads, check valve
243 prevents cylinder pressure acting up through the metering
chamber 232 from affecting the fuel metering since the supply fuel
is not metered against cylinder pressure.
Injector cup 158 also includes a radially extending drain passage
244 and a longitudinally extending drain passage 246 communicating
with passage 244. Passage 246 connects with a drain passage (not
shown) which communicates with annular chamber 202. In this manner,
timing fluid drained from timing chamber 180 into annular chamber
202 is directed through passage 246 into drain passage 244. This
fluid is used to lubricate metering plunger 178 and to carry away
any combustion gases leaking into metering chamber 232. An annular
recess 248 formed in metering plunger 178 communicates with drain
passage 244 when metering plunger 178 is in its innermost position
to insure lubrication fuel is supplied between plunger 178 and bore
216.
The operation and advantages of the individual timing and injection
fuel metering system of FIG. 1 using the open nozzle fuel injector
of FIG. 5 as the injectors in each set 14, 16, are substantially
the same as previously discussed with respect to the closed nozzle
injector of FIG. 2 except for the operation of open nozzle unit
injector 150 which will now be discussed in detail. FIG. 5
illustrates open nozzle unit injector 150 at the beginning of the
injection mode with timing plunger 174 at its outermost position
against coupling 167 and metering plunger 178 in its outermost
position with outer spring keeper 222 held against outer barrel 154
by spring 230. As the cam (not shown) continues to rotate causing
link 170 and coupling 167 to move inwardly against spring 172,
timing plunger 174 is moved inwardly compressing the timing fluid
in timing chamber 180 and ending the previous timing period. The
compressed timing fluid in chamber 180 forms a solid hydraulic link
between timing plunger 174 and intermediate plunger 176. Further
movement of timing plunger 174 inwardly forces intermediate plunger
176 against the outermost portion of metering plunger 178 thereby
moving metering plunger 178 inwardly against the spring pressure of
spring 230. During the inward movement of metering plunger 178,
fuel delivered to metering chamber 232 during the previous metering
period is compressed and injected through injection orifices 233
formed in the lower end of cup 158. Injection will continue until
the metering plunger 178 bottoms in injector cup 158 while, at the
same time, annular groove 196 of intermediate plunger 176 aligns
with spill orifice 198 allowing timing fluid to spill from timing
chamber 180 through axial passage 192, radial passage 194, annular
groove 196 into spill port 200. Spill ring 204 opens to allow
timing fluid in spill port 200 to flow out of the injector through
drain port 206. Timing plunger 174 continues to be forced inwardly
by the rotation of the cam (not shown) forcing timing fluid out of
chamber 180 until timing plunger 174 abuts intermediate plunger
176. At this point, plungers 174, 176 and 178 are mechanically held
in an innermost position as link 170 rides on the outer base circle
of the cam (not shown).
When link 170 reaches the ramp portion of the cam and begins moving
outwardly, spring 230 will force metering plunger 178, intermediate
plunger 176 and timing plunger 174 outwardly until upper spring
keeper 222 abuts outer barrel 154 terminating the upward movement
of metering plunger 178. Upward movement of metering plunger 178
opens supply orifice 242 marking the beginning of the metering
period within which fuel may be metered into metering chamber 232.
Also, upward movement of timing plunger 174 marks the beginning of
the timing period during which timing fluid may be delivered to
timing chamber 180 since at least one of passages 184 are open to
annular recess 190 and spill orifice 198 is blocked by intermediate
plunger 176. As previously discussed, the timing event during which
timing fluid is delivered to timing chamber 180 is controlled by
the opening time of the respective timing fluid control valves 18,
22. Likewise, the metering event during which fuel is delivered to
metering chamber 232 is controlled by the opening time of injection
fuel control valves 20, 24. The metering and timing events are
completed before timing plunger 174 begins its inward movement
which marks the end of both the metering and timing periods during
which the metering and timing events must occur. Therefore, the end
of the metering and timing periods are defined by the cam profile
which controls the inward movement of link 170 and timing plunger
174.
FIG. 6 illustrates another embodiment of the present invention
which is the same as the embodiment of FIG. 1 except that a flow
control valve 250 is positioned downstream of each control valve
18, 20, 22, 24 to provide a fixed flow rate during metering and
timing events. Each flow control valve 250 receives fluid or fuel
from a respective timing fluid or injection fuel control valve 18,
20, 22, 24 and insures that a fixed flow of timing fluid or fuel is
delivered to a respective injector independent of fluid pressures
upstream and downstream of the flow control valve 250.
FIG. 7 represents another embodiment of the present invention which
is the same as the embodiment shown in FIG. 1 except that a
pressure regulator 252 is positioned in a bypass circuit 254
downstream of supply pump 12. Pressure regulator 252 controls the
supply pressure to control valves 18, 20, 22, 24 by controlling the
amount of fuel allowed to flow through bypass circuit 254 to the
supply side of supply pump 12. Based on a pressure signal from a
pressure sensor 256 sensing the fuel pressure downstream of supply
pump 12 and other engine operating conditions, ECU 38 controls the
pressure regulator 252 to vary the amount of bypassed fuel and thus
the fuel supply pressure. Pressure regulator 252 is especially
desirable during periods of low engine speed wherein a much smaller
amount of fuel must be metered by the control valves. If the supply
pressure were to remain constant, the control valves would be
required to open and close extremely quickly to provide the proper
amount of metered fuel. By decreasing the supply fuel pressure
during periods of low speed operation, the operating requirements
of the solenoid and its associated circuitry are decreased while
maintaining effective and predictable control of fuel injection
timing and metering.
FIG. 8 represents yet another embodiment of the present invention
which includes a fuel injector 260 supplied with fuel for injection
by fuel metering system 262. Fuel metering system 262 is equivalent
to the injection fuel control valves 20, 24, supply pump 12, ECU 38
and associated common rail portions 46, 48 illustrated in FIG. 1
and described hereinabove. Therefore, fuel metering system 262 also
supplies fuel to two other fuel injectors (not shown) associated
with a first set of injectors including injector 260 and to a
second set of three fuel injectors (not shown). However, the timing
fluid control portion of the metering system of FIG. 1 is replaced
by a timing control valve 264, high pressure reservoir 266 and a
high pressure pump 268. Each injector of each set of injectors
includes its own timing control valve 264 receiving high pressure
timing fluid from common reservoir 266 and common high pressure
pump 268. Fuel injector 260 is of the closed nozzle type having the
conventional tip valve element 270 spring biased against injector
orifices 273 and positioned in a nozzle cavity 272 for receiving
fuel from a metering chamber 274. Fuel is supplied from the fuel
metering system 262 to metering chamber 274 via a supply passage
276 and inlet check valve 278.
The upper timing portion of injector 260 includes a large axial
bore 280 and a smaller axial bore 282 positioned inwardly of and
axially aligned with bore 280. A plunger 284 includes an upper
section 286 mounted for reciprocal movement in bore 280 and a lower
section 288 mounted for reciprocal movement in bore 282. The
outermost end of upper section 286 is positioned in a cavity 290
adapted to receive timing fluid from control valve 264. The
innermost end of upper section 286 is positioned in a second cavity
292 which is connected to a timing fluid drain 294 by a drain
passage 296.
Timing fluid control valve 264 is a three-way solenoid valve which
may be positioned to allow fuel to flow from reservoir 266 into
cavity 290 to effect the inward movement of plunger 284 causing
fuel injection at the appropriate time during each cycle of the
engine. Control valve 264 may also be positioned to connect cavity
290 with drain 294 thus equalizing the pressure in cavities 290 and
292.
During operation, control valve 264 is positioned to allow high
pressure timing fluid into cavity 290 thereby forcing plunger 284
inwardly preventing fuel from the fuel metering system from
entering the metering chamber 274 until just before the time period
for injection by injector 260. At this time, timing control valve
264 is positioned to block the flow of timing fluid from reservoir
266 while connecting cavity 290 to drain 294 thus starting the
metering period. The injection fuel control valve associated with
injector 260 may then be operated to allow fuel to pass through
passage 276 into metering chamber 274. The pressure of the supply
fuel entering metering chamber 274 forces plunger 284 outwardly
until the associated fuel control valve closes thus terminating the
metering event. Timing control valve 264 may then be positioned to
allow high pressure timing fluid from reservoir 266 to flow to
cavity 290. The high pressure of the timing fluid acting on the end
of plunger 284 positioned in cavity 290 forces plunger 284
inwardly. Lower section 288 of plunger 284 compresses fuel in
metering chamber 274 and, consequently, nozzle cavity 272 until the
fuel pressure in nozzle 272 exceeds the spring bias pressure of tip
valve element 270 causing element 270 to move outwardly to allow
fuel to pass through the injector orifices 273 in the combustion
chamber (not shown). When injection is complete, timing control
valve 264 is returned to the position blocking the flow of timing
fluid from reservoir 266 and connecting cavity 290 to drain 294
thus positioning the injector for fuel metering during the next
cycle of the engine.
FIG. 9 illustrates a further embodiment of the present invention
which is the same as the embodiment shown in FIG. 1 except that the
timing fluid supply paths 300 and 302 are fluidically separate from
the fuel supply paths 304 and 306 to allow lubrication oil to the
used as the timing fluid. An engine lube oil pump 308, which is
preferably a gear pump, draws fuel from a reservoir 310 and directs
it through a supply passage 312 connected to timing fluid supply
paths 300, 302. A separate fuel supply pump 314 draws fuel from a
reservoir 316 for delivery to the injectors 14, 16 via a supply
passage 318, fuel supply paths 304, 306, common rail portions 46,
48 and fuel metering circuits 52 as governed by the position of
injection control valves 20, 24 as discussed hereinabove with
respect to the embodiment of FIG. 1. The delivery of lube oil
timing fluid to the injectors 14, 16 via common rails 42, 44 and
timing circuits 50 is also controlled by the operation of timing
fluid control valves 18, 22 as discussed hereinabove with respect
to FIG. 1. Lube oil spilling from the timing chamber of each
injector 26 is returned to the engine lube oil reservoir 310 via a
drain passage 320.
The use of lubrication fluid as a timing fluid in a lubrication
timing fluid circuit completely separate from the fuel metering
circuit serves several important functions. First, by using
lubrication fluid instead of fuel as the timing fluid, the fuel
supply demanded by each injector on a cycle by cycle basis is
reduced significantly which reduces the amount of hot fuel returned
to the fuel supply tank downstream of the fuel drain. As a result,
the fuel temperature in the fuel supply tank is reduced
significantly minimizing undesired fuel evaporation and avoiding
the need for expensive fuel coolers.
Referring to FIGS. 2 and 5, the lubrication fluid provides improved
lubrication of the timing plunger 76, 174 as it reciprocates in the
plunger cavity 66, 162. Third, a leakoff passage or groove 83, 85
is not needed between the timing chamber 86, 180 and upper cavity
68, 164 because the lubrication fluid that escapes from the outer
end of the injector body is simply released into the rocker housing
of the engine where engine lubrication oil already exists.
Therefore, any leak-by lubrication fluid can likewise be used to
lubricate coupling 72, 167 and any other linkage in the rocker
housing. Fourth, the lubrication fluid functions to cool the fuel
injector internals as it flows through the lubrication fluid timing
circuit during each cycle.
Industrial Applicability
While the individual timing and injection fuel metering system of
the present invention is most useful in a compression ignition
internal combustion engine, it can be used in any combustion engine
of any vehicle or industrial equipment in which accurate control
and variation of the timing of injection and the metering of the
proper quantity of fuel is essential.
* * * * *